California Department of Fish and Wildlife

DRERIP Conceptual Models

What are Conceptual Models?

Conceptual models use diagrams, narratives and/or tables to represent a set of causal relationships in a simplified manner (see example below). They can be used to develop, refine and document a common understanding of ecosystems, including assumptions about intended outcomes from potential actions, such as restoration. Conceptual models can provide a basis for incorporating new information and continually improving our knowledge of the system.

A formalized approach to the development of conceptual models for the Sacramento-San Joaquin Delta has been developed under the auspices of the Delta Regional Ecosystem Restoration Implementation Plan (DRERIP), a component of ERP. The fundamental approach to modeling employed through this effort is a "driver-linkage-outcome" approach that uses deterministic models of ecosystem components linked together with cause-and-effect relationships of interacting variables and outcomes. Additional information can be found on the "driver-linkage-outcome" page. Two types of conceptual models have been generated through this process: species life history models and ecosystem models (processes, habitats, and stressors).

An example of a DRERIP life-history conceptual model for Chinook salmon is included below (Source: Williams 2010). The life history models identify key environmental factors that influence whether individuals of the species survive from one stage of development to the other. This model shows factors that have a positive or negative influence in the likelihood that Chinook salmon eggs will survive to fry.

How does the ERP utilize Conceptual Models

Clearly articulated conceptual models that specify key state variables, describe their dynamic interrelationships, and project consequences of alternative management actions are a key component of adaptive management (Walters 1986). Models are extremely valuable for formalizing the link between management objectives and proposed actions to clarify how and why each action is expected to contribute to those objectives. They also provide a venue through which to identify areas of uncertainty, assess the likelihood of success, identify potential restoration actions, develop expectations and performance measures, and define monitoring needs.

The DRERIP Conceptual Models were developed for the purpose of showing the characteristics and dynamics of the Delta ecosystem, qualitatively predicting ecosystem and species response to specific changes in ecosystem attributes, and providing the science-based information needed to determine whether a restoration action would result in (or contribute to) a desired management outcome. These models are valuable tools themselves, but were designed to provide information for use in structured assessments of proposed restoration actions through the DRERIP Action Evaluation Procedure and Decision Support Tool.

Salmon Conceptual Model Diagram

Click on the diagram above to view a larger image

Legend for DRERIP Conceptual Models

Source: Williams 2010

To see and download the DRERIP conceptual models and find out more about how they are used, see the links below and in the box to the right.

See the current DRERIP Conceptual Models